1. Field of the Invention
The present invention relates to a backlight unit of a liquid crystal display, and more particularly to a backlight unit of a liquid crystal display that is adaptive for arranging a wire for supplying a driving current connected to a common electrode to be penetrated a piece provided at the inside portion.
2. Description of the Related Art
Generally, a liquid crystal display devices are widely used due to its characteristics of light weight, thin profile, low power consumption, etc. As a result, the liquid crystal display device is used in office automation equipment, audio/video equipment, etc. The liquid crystal display device controls the amount of light in accordance with a signal applied to a plurality of control switches that are arranged in a matrix, thereby displaying a desired picture on a screen.
In this way, the liquid crystal display device is not a self luminous display device, thus it requires a separate light source such as a backlight.
Backlights may be largely classified as a direct type and an edge type in accordance with the location of a light source. The edge type backlight has a light source installed at the edge of one side of a liquid crystal display device, and the edge type backlight irradiates light from the light source to a liquid crystal display panel through a light guide plate and a plurality of optical sheets. The direct type backlight has a plurality of light sources disposed directly under the liquid crystal display device, and the direct type backlight irradiates light from the light sources to the liquid crystal display panel through a diffusion plate and a plurality of optical sheets. Recently, the direct type backlight which has improved brightness, light uniformity and color purity versus the edge type backlight, is more often used in LCD TVs.
A cold cathode fluorescent lamp (hereinafter, referred to as “CCFL”) and an external electrode fluorescent lamp (hereinafter, referred to as “EEFL”) are used for a light source for a backlight.
Referring to FIG. 1, a related art EEFL is comprised of a glass tube 10, a phosphor 12 coated at an inner wall of the glass tube 10, inactive gasses 14 (or a discharge gas) injected into an internal of the glass tube 10, and an external electrode 16 installed at both external edges of the glass tube 10.
The glass tube 10 is a cylindrical type, and has an internal diameter of about 1.6 mm and an external diameter of about 2.0 mm. A length of the glass tube 10 is about 50 mm to 400 mm.
Ne and Ar are mixed in the inactive gasses 16 in a constant ratio, and a small quantity of Hg is mixed in the inactive gasses.
If an AC voltage from an inverter is applied to a high-level voltage electrode and a low-level voltage electrode, an electron is emitted from the low-level voltage electrode of the EEFL to collide with the inactive gasses of the internal of the glass tube, thus an amount of the electron is increased exponentially. As a result, the inactive gasses are excited by the electrons to emit the ultraviolet rays. The ultraviolet rays collides with the phosphor coated at the inner wall of the glass tube to emit a visible rays.
A backlight unit of a related art liquid crystal display device using the EEFL will be described as follows.
FIG. 2 is a perspective view showing a backlight unit of the related art liquid crystal display.
Referring to FIG. 2, a related art backlight unit 100 includes a plurality of lamps 110 arranged at a rear surface of a liquid crystal display panel, a reflection sheet 120 arranged at lower portion of the plurality of lamps 110, a cover bottom 130 to which the reflection sheet 120 is attached, and a first and second side bottoms 140 and 150 arranged at an internal of the cover bottom 130 and located to be symmetrical with both sides of the reflection sheet 120.
Herein, a first and second common electrodes 160 and 170 are formed at an internal of the backlight unit 100. The first common electrode 160 is formed to be adjacent to the first side bottom 140. The second common electrode 170 is formed to be adjacent to the second side bottom 150.
Furthermore, the first common electrode 160 is supplied with a driving current common voltage via a first wire 180 for supplying a driving current. In this case, the first wire 180 for supplying the driving current is connected to the first common electrode 160. The second common electrode 170 is supplied with a driving current common voltage via a second wire 190 for supplying a driving current. In this case, the second wire 190 for supplying the driving current is connected to the second common electrode 170. Herein, the first wire 180 is arranged to be exposed at an external of the first side bottom 140, and the second wire 190 is arranged to be exposed at an external of the second side bottom 150.
As described above, since the first and second wires are arranged to be exposed at the external, the lengths of the first and second wires for supplying the driving current are unnecessarily lengthened. As a result, in the related art backlight unit, a resistance disturbing a supply of the driving current is increased, and a volume of the product is getting bigger. Furthermore, inconvenience is caused by the first and second wires which are exposed at the external upon manufacturing of the related art backlight unit.